1. Field of the Invention
The field of this invention is analyte determination, particularly electrochemical analyte determination and more particularly the electrochemical determination of blood analytes.
2. Background
Analyte detection in physiological fluids, e.g. blood or blood derived products, is of ever increasing importance to today""s society. Analyte detection assays find use in a variety of applications, including clinical laboratory testing, home testing, etc., where the results of such testing play a prominent role in diagnosis and management in a variety of disease conditions. Analytes of interest include glucose for diabetes management, cholesterol, and the like. In response to this growing importance of analyte detection, a variety of analyte detection protocols and devices for both clinical and home use have been developed.
One type of method that is employed for analyte detection is an electrochemical method. In such methods, an aqueous liquid sample is placed into a reaction zone in an electrochemical cell comprising two electrodes, i.e. a reference and working electrode, where the electrodes have an impedance which renders them suitable for amperometric measurement. The component to be analyzed is allowed to react directly with an electrode, or directly or indirectly with a redox reagent to form an oxidizable (or reducible) substance in an amount corresponding to the concentration of the component to be analysed, i.e. analyte. The quantity of the oxidizable (or reducible) substance present is then estimated electrochemically and related to the amount of analyte present in the initial sample.
In electrochemical analyte detectors used to practice the above described methods, it is often desirable to modify the surface of the metal electrodes to be hydrophilic. A variety of different techniques have been developed to modify the surfaces of metal electrodes. However, such surface modified electrodes tend to have limited storage life, thus limiting their potential applications.
As such, there is continued interest in the identification of new methods for modifying metallic electrode surfaces for use in the electrochemical detection of analytes. Of particular interest would be the development of a method which resulted in a storage stable hydrophilic surface that provided rapid wicking time and did not interfere with the electrochemical measurements of the electrode.
Relevant Literature
U.S. Patent documents of interest include: U.S. Pat. Nos. 5,834,224; 5,942,102 and 5,972,199. Other patent documents of interest include WO 99/49307; WO 97/18465 and GB 2 304 628. Other references of interest include: Dalmia et al, J. Electroanalytical Chemistry (1997) 430: 205-214; Nakashima et al., J. Chem. Soc. (1990) 12: 845-847; and Palacin et al., Chem. Mater. (1996) 8:1316-1325.
Electrochemical test strips and methods for their use in the detection of an analyte, e.g. glucose, in a physiological sample, e.g. blood, are provided. The subject test strips have a reaction area defined by opposing metal electrodes separated by a thin spacer layer. The metal surface of at least one of the electrodes is modified by a homogenous surface modification layer made up of linear self-assembling molecules having a first sulfhydryl end group and a second sulfonate end group separated by a short chain alkyl linking group, where 2-mercaptoethane sulfonic acid or a salt thereof is preferred in certain embodiments. The subject electrochemical test strips find application in the detection of a wide variety of analytes, and are particularly suited for use the detection of glucose.